The ability to follow or to resolve temporal changes is crucial importance for auditory perception and communication. The overall objective of this project is to characterize this ability in normal, cochlear-impaired, and electrically stimulated hearing and to evaluate possible mechanisms underlying this ability and its impairment. More specifically, the objectives are: (1) to address the fundamental questions of how auditory frequency analysis, spectral frequency region, and peripheral hearing loss determine and affect temporal processing of envelope information; (2) to determine and describe how the ability to detect certain envelope periodicities is affected by the presence of other periodicities; (3) to describe the basic psychophysical properties of cross- channel temporal resolution using envelope coherence detection as the basic task; (4) to delineate the basic psychophysical characteristics of intensity discrimination and modulation detection of single-channel electrical stimulation in patients with cochlear implants; (5) to pursue both experimentally and theoretically an unexpected and potentially important phenomenon involving dynamic maskers; (6) to study in detail the consequences of cochlear hearing loss on the ability to discriminate and detect intensity differences and changes. This project will provide information of fundamental importance for understanding certain dynamics properties and processes in normal, cochlear-impaired, and electrically stimulated hearing. The proposed research, both experimental and theoretical, will lead to a better understanding of the underlying mechanisms and the consequences of hearing loss on basic dynamic processes and, together with the other projects in this CRCG, may lead to improved detection and differentiation of hearing disorders. The proposed work on electrically-stimulated hearing will provide much-needed basic information about the auditory processing abilities of cochlear-implant patients. It will also provide a rational basis for designing signal-processing schemes for use with electrical stimulation and may also help to better understand the role of the auditory periphery in normal and cochlear-impaired acoustic hearing.